Most trucking stocks got a bounce on Thursday as Wall Street extended its rally for a second day — and that was before J.B. Hunt (NASDAQ:JBHT) reported blockbuster first-quarter earnings after the market closed. But before you decide to join this convoy, be prepared for a speed trap ahead: rising diesel-fuel prices.

Granted, that contrarian advice seems strange given JBHT’s eye-popping quarterly report. Earnings per share (EPS) jumped by 42% year-over-year, to 57 cents ($67.7 million), and revenue rose more than 16%, to nearly $1.2 billion. The company’s results beat Wall Street estimates for both the top and bottom lines.

The biggest star was J.B. Hunt’s intermodal segment — freight in containers that can move by truck, ship or rail. It contributed heavily to the trucking company’s earnings, rising 20% in the quarter. JBHT’s third-party-logistics segment, Integrated Capacity Solutions, grew by 30% in the quarter.

Despite the positive news, there may be potholes ahead for J.B. Hunt and its peers.

In the company’s truck segment, revenue rose by 8%, but profit fell by 16%. While JBHT was able to reduce maintenance costs and boost fuel efficiency, pricier diesel fuel — as well as higher costs for labor and safety compliance — offset those gains.

J.B. Hunt’s earnings are particularly important because it acts as a bellwether for other companies in a sector that will report earnings in the coming weeks.

JBHT’s market cap is two to three times that of other major truckers, including Landstar (NASDAQ:LSTR), Con-Way (NYSE:CNW), Heartland Express (NASDAQ:HTLD), Old Dominion Freight Line (NASDAQ:ODFL), Werner Enterprises (NASDAQ:WERN) and Knight Transportation (NYSE:KNX).

It’s no secret that expensive diesel fuel is the bane of truckers’ existence. Because global diesel-fuel demand is putting pressure on refining capacity and the U.S. is switching to low-sulfur diesel, prices have risen rapidly. It doesn’t help that federal excise taxes are six cents higher per gallon than gasoline.

While truckers can and do pass on fuel costs to shippers in the form of surcharges, there are limits to what pressured shippers will bear. It doesn’t help that the trucking industry’s biggest competitor — railroads — can carry a ton of freight 423 miles on a single gallon of diesel.

Anything close to that would be an unmitigated disaster for the trucking industry — and for investors in the sector’s stocks.

The bottom line: Trucking is a tough business — high capital expenses, expensive regulations and a fate inextricably linked to the economy’s well-being. But diesel-fuel prices are eating the sector’s lunch. In addition to rising fuel costs, trucking companies are struggling to retain drivers — the driver turnover rate at large fleets now stands at 88%.

Trucking stocks have risen an average of 45% since last fall. If you’re already in some of the stronger names like JBHT, ODFL or LSTR, I’d hold, but in my opinion, there are too many wild cards to establish a new long position.

As of this writing, Susan J. Aluise did not hold a position in any of the stocks named here.